The present invention relates to a photographic printing method and more particularly to a photographic printing method which determines a print exposure amount in accordance with principal object distance information recorded on a recording medium, such as photographic film when the frame image was taken.
In making photographic prints the print exposure amount is determined in accordance with a measured average transmittance density of a frame image recorded in a photographic film. This exposure control is called a large area transmittance density (LATD) method by which about 70% of frame images can be printed while providing proper density and color balance of a principal image or image of principal object (subject). In order to improve the ratio of proper prints to improper prints, recently a scanner has been used for measuring each point on a frame. With such a photographic printer equipped with a scanner, a print exposure amount determined by the LATD method is corrected by using characteristic values including maximum and minimum transmittance densities, and average transmittance densities of virtually divided areas of a frame, which are obtained by measuring transmittance densities (hereinafter simply called densities) of respective points of the frame.
The above-described conventional photographic printing methods determine a print exposure amount suitable for a particular scene by presuming the nature of the scene on the basis of the density of each point on the frame recorded in a photographic film. However, using only the density of each point on a photographic film makes it difficult to discriminate the nature of each scene correctly determine a precise print exposure amount, and obtain a properly finished principal image.
For instance it is necessary to determine the print exposure amount of a landscape scene so as to provide proper density over the whole area of the frame. In contrast, it is necessary to determine the print exposure amount of a figure scene so as to provide proper density of the figure, even at the cost of the improper density of the background image to some degree. However, it is difficult to discriminate between two types of such scenes by using only the density. As a result the density of a scenery image of the landscape scene is too low and the density of a figure image of the figure scene is too high. It is preferable to use a different print exposure amount between a figure scene with only the upper half figure and a figure scene with the whole figure.
Another method is known whereby characteristic values are derived by using the densities of selected measurement points among a plurality of points within a frame. For example according to Japanese Patent Publication No. 59-29848 characteristic values are derived by using a plurality of weighted densities of pairs of two adjacent points having a density difference larger than a predetermined value. According to Japanese Patent Laid-open Publication No. 59-65835. the densities of points having a small density change in a direction from a peripheral portion to a central portion of a frame are excluded in deriving characteristic values.
These methods attempt to presume a principal image by excluding the measurement points having a small contrast. However a principal image does not necessarily have a large contrast, so that these methods also have difficulty in obtaining a principal image having proper density.
There also are two types of scenes which require increased and decreased print exposure amounts, respectively, and cannot be discriminated by using a scanner. For example, a scene taken with a flash at night and a scene taken with underexposure both have a low average transmittance density but the densities of the principal images are different from each other. It is difficult for the scanner photometry to discriminate a principal image and determine a proper print exposure amount for these two scenes. Also, a scene having a principal object in a bright background (such as a white wall, a white sliding door and the like) and taken with a flash or taken synchronously with a flash in daylight, and a scene taken with rear light, both have a high density of background, but the density differences between the backgrounds and principal images are different from each other, and the densities of the principal images are different from each other. The scanner photometry cannot discriminate the principal images of these two types of scenes and cannot determine their proper print exposure amounts.
A method of controlling the exposure amount of a photographic camera in accordance with an object distance also is known. For example, Japanese Patent Laid-open Publication No. 59-31933 describes an exposure control method providing a plurality of range finding areas to measure the distances of objects within the areas. The shortest distance is used as that of a principal object, whereas the other distances are used as those of a background. The brightness of the principal object is compared with that of the background to discriminate a scene and select an exposure program. Also, Japanese Patent Laid-open Publication No. 62-58228 describes an exposure control method whereby a scene is divided into two range finding areas to measure the brightness of each area, and the lower brightness area is selected for the exposure control.
Japanese Patent Laid-open Publication No. 62-255921 describes a method whereby range finding for a scene is carried out at a plurality of range finding areas, and the photometry method is changed in accordance with the range finding results. Specifically, if there is one range finding area in which an object was detected, spot photometry is carried out. If there are a plurality of such range finding areas and an object is not present within the central area, then photometry emphasizing the central area is carried out. If an object is not present within the central area, average photometry at a predetermined area is carried out.
The above methods are applied only to a photographic camera, and not to a photographic printer as the printer is not directed to the object. Also, it should be noted that there are a plurality of images within one frame which may be classified, in accordance with the intent of a photographer, into a primary principal image, a secondary principal image a background image, a foreground image and the like. These images are given different priorities by a photographer, so that it is preferable to print in accordance with the priority order. However at the photographic printer, it is impossible to determine such priority order for printing the images in accordance therewith.